PROJECT SUMMARY/ABSTRACT Substance use, HIV risk behaviors, and criminal activity have created numerous challenges for juvenile justice systems. Addressing unmet substance use disorder (SUD) and mental health needs among the high priority population of justice-involved youth requires a coordinated effort between juvenile justice and behavioral health agencies to support evidence based screening, assessment, referral, and linkage to care. This coordinated approach is unfamiliar to most juvenile justice and behavioral health agencies that traditionally operate as separate silos of probation/monitoring and substance use/health services delivery. Part of this disconnect may be the result of financial concerns regarding the additional resources required by juvenile justice and behavioral health agencies to ensure youth receive the recommended continuum of evidence based services. A second part of this disconnect may relate to the broader context of how effectively and efficiently the juvenile justice system is able to integrate with the behavioral health system. Few studies have examined organizational, environmental, and other system barriers to improved behavioral health services delivery in juvenile justice settings. To address this knowledge gap, this proposal takes advantage of a unique opportunity to work with Juvenile Justice -Translational Research on Interventions for Adolescents in the Legal System (JJ- TRIALS), a multisite cooperative research initiative funded by the National Institute on Drug Abuse. The JJ- TRIALS research protocol features two randomly assigned implementation interventions, Core and Enhanced, which are focused on improving screening, assessment, referral, and linkage to behavioral health services among juvenile justice youth with SUD. To broaden the research impact of JJ-TRIALS, the current proposal seeks funding to examine how the variation in environmental and organizational characteristics ? in addition to factors associated with implementing the Core and Enhanced interventions ? impact behavioral health services utilization and outcomes (e.g. recidivism, substance use) across different juvenile justice and behavioral health settings. Aim 1 is to develop an overlapping systems analysis framework to identify organizational and environmental factors associated with uptake and penetration of evidence based practices for SUD among diverse juvenile justice settings. Aim 2 is to analyze the marginal impact of system factors, in addition to randomization to Core or Enhanced implementation interventions, on behavioral health services utilization and youth outcomes. The results of the proposed research will provide the first multisystem and multiagency perspective on the role of funding, implementation resources, agency characteristics, and other key factors in facilitating the adoption of evidence based practices targeting SUD and other risky behaviors among justice involved youth.